Patent Application
20140315679
The invention relates generally to a stacked planetary gear set, and more particularly to an inner single pinion and an outer double pinion arrangement in a stacked planetary gear set.
The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
In order to increase fuel efficiency and improve performance, automatic transmissions have been developed having eight, nine, and ten or more speeds. Transmissions providing eight or more speeds oftentimes have four or more planetary gear sets arranged axially. However, the need to reduce packaging size, weight, and cost of these transmissions remains essentially constant. One solution to reduce the axial length of these transmissions is to employ a stacked or nested planetary gear set. A stacked or nested planetary gear set includes an inner sun gear that meshes with a first set of planet gears, a sun/ring or intermediate gear that meshes with the first set of planet gears and an outer, second set of planet gears, and a ring gear that meshes with the second set of planet gears. The first and second set of planet gears are supported for rotation on pinion pins that are connected to a planet carrier.
While these stacked planetary gear sets are useful for their intended purpose, there is a need in the art for stacked planetary gear sets that are able to accommodate double planetary pinion designs without unnecessarily increasing axial or radial length of the transmission.
A stacked or nested planetary gear set for a transmission is provided. The planetary gear set includes a carrier member supporting for rotation a first set of planet gears, a second set of planet gears, and a third set of planet gears, wherein each of the second set of planet gears are intermeshed with the third set of planet gears. A first sun gear is intermeshed with each of the first set of planet gears. A first ring gear is intermeshed with each of the first set of planet gears. A second sun gear is directly connected to the first ring gear and is intermeshed with each of the second set of planet gears. A second ring gear is intermeshed with each of the third set of planet gears.
In one example of the planetary gear set, the second set of planet gears are disposed radially outward of the first set of planet gears and wherein the third set of planet gears are disposed radially outward of the second set of planet gears.
In another example of the planetary gear set, the first set of planet gears is disposed at intervals around the first sun gear.
In another example of the planetary gear set, the second set of planet gears is disposed at a radial offset of between 0 and 120 degrees from the first set of planet gears.
In another example of the planetary gear set, the second set of planet gears is disposed at a radial offset of 45 degrees from the first set of planet gears.
In another example of the planetary gear set, the third set of planet gears is disposed at a radial offset from the second set of planet gears.
In another example of the planetary gear set, the second set of planet gears are at a distance r1 from a rotational axis of the planetary gear set, the third set of planet gears are at a distance r2 from the rotational axis, and wherein r1 is less than r2.
In another example of the planetary gear set, the first ring gear and the second sun gear are formed on a common member, the first ring gear is disposed on an inner peripheral surface of the common member and the second sun gear is disposed on an outer peripheral surface of the common member.
In another example of the planetary gear set, the first ring gear is axially offset from the second sun gear.
In another example of the planetary gear set, the first ring gear is formed on an inner peripheral surface of a first member, the second sun gear is formed on an outer peripheral surface of a second member, and the first member is directly connected to the second member.
In another example of the planetary gear set, the first ring gear is in complete axial alignment with the second sun gear.
In another example of the planetary gear set, the first ring gear is axially offset from the second sun gear.
Further features, aspects and advantages of the present invention will become apparent by reference to the following description and appended drawings wherein like reference numbers refer to the same component, element or feature.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way.
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.
With reference to
The first sun gear 12, the first ring gear 16, the second sun gear 18, the second ring gear 20, and the carrier member 14 may each be connected to various other components, indicated schematically by reference numbers 28A-D, respectively. These components 28A-D may include, for example shafts, countershafts, layshafts, sleeve shafts, clutches, brakes, turbine shafts, a transmission housing, or other planetary gear sets, to name but a few.
With reference to
Measured from the axial centers of the planet gear pins, the set of inner planet gears 22 are disposed at ninety degree intervals around the inner sun gear 12. It should be appreciated that the inner planet gears 22 may be spaced at other intervals depending on various factors including tooth count of the gears and the number of planet gears. The first set of outer planet gears 24A are radially offset from the set of inner planet gears 22 at an angle “theta”. Theta varies from 0 degrees to 120 degrees, and in one example about 45 degrees is preferred. In order to reduce the radial dimensions of the stacked planetary gear set 10, the second set of outer planet gears 24B are radially offset from the first set of outer planet gears 24A at an angle “phi”. Phi varies from 0 degrees to 90 degrees. Measured from a central origin “o” located at the radial center of the stacked planetary gear set 10 to the axial centers of the planet gear pins, the first set of outer planet gears 24A are located at a radial distance r1 from the origin. The second set of outer planet gears 24B are located at a radial distance r2 from the origin. In order to reduce the radial dimensions of the stacked planetary gear set 10, r1 is less than r2 and angle “phi” is generally not equal to 0 degrees. In other words, the second set of outer planet gears 24B are offset from and partially radially outward of the first set of outer plant gears 24A.
Turning to
With reference to
The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.
